A conventional mold assembly for making paper products, such as paper bowls and paper cups, generally includes a top mold with a female mold and a lower mold with a male mold which matches a concavity in the female mold. Paper material is filled between a gap between the inner periphery of the concavity and the male mold. There are several tiny paths defined in the top mold and communicating with the female mold so as to provide negative pressure so suck the paper product from the male mold to the inner periphery of the concavity of the female mold. The paper product is then shifted to another place to dry it up. It is noticed that the positions where the paths are located will cause bumps and/or thinner areas on the paper products because of the suction. This reduces the durability of the products. Besides, before the paper product is completely dried, it is shifted to be heated will also make the surface of the paper product be rough.
The present invention intends to provide a mold assembly for making paper products wherein the paths are located at the boundary surfaces between the cores and the female mold so that the paper product has annular flanges at ridges thereof rather than at the surface.